A legged robot that is provided with a body trunk (the “body trunk” may simply be referred to as the “trunk” hereinafter) and a pair of legs that are connected to the trunk so as to be able to rotate is being developed. Each of the legs is provided with a plurality of links and joints that connect the adjacent links together so as to be able to rotate. Actuators such as motors, for example, are provided in the leg connecting portions, which connect the trunk and the legs so as to be able to rotate, and in the joints of the legs, and the legged robot walks by appropriately controlling the actuators. Generally, the leg connecting portion has a rotation axis at which the leg is rotated around the pitch axis with respect to the trunk. When the entire leg rotates around the pitch axis with respect to the trunk, the foot of the leg moves back and forth with respect to the trunk. It is possible to realize a long step length that takes maximum advantage of the entire lengths of the legs by rotating each of the legs alternately around the pitch axis with respect to the trunk.
Such a legged robot is disclosed in Japanese Patent Application Publication No. 2005-186650 (Patent Document 1). The legged robot disclosed in Patent Document 1 is provided with a trunk in which a person can ride, and a pair of legs. Each of the legs is connected at the bottom of the trunk so as to be able to rotate with respect to the trunk. Each of the legs is connected so as to be able to rotate around the pitch axis with respect to the trunk.